Copyrtgllr 1981S. American MedlcaJ AastJciatIon Symptoms of Anxiety and Depression in a Volunteer Twin Population The Etiologic Role of Genetic and Environmental Factors

• We examined the etlotoglc role of genetic and environmen-tal factors In 14 symptoms of anxiety and depression reported by 3,798 pairs of adult twins from the Australian National Health and Medical Research Council 1Wln Register. Multifac-torial multlple-threshotd models fH the Individual symptom scores well. For a substantial majority of the symptoms, the varlanca In liability was beat explained by only genetic factors and envlronmentallnfluencaa specific to the Individual, where 33 % to 46 % of the variance was due to genetic factors. For four symptoms, It was not po_lble to choose deflnltlvaly between models that, In addition to specHic environment.. Included genetic vs familial environmental effects. These results pro-vide strong evidence for the role of genetiC factors In the etiology of symptoms of anxiety and depression 88 reported In a general population. Evidence for an etIotoglc rote of familia